Fix proguard issue with fusion table.

Fusion table depends on google-api-client-1.2.2.alpha.jar.
Proguard needs to be set correctly for the google-api-client library.

Tested a release version and is able to send a track to fusion table.

MyTracks/default.properties

@@ -13,7 +13,5 @@ split.density=false
 target=Google Inc.:Google APIs:13
 android.library.reference.1=../MyTracksLib/
 
-# ProGuard is turned off while we investigate the removal of code that
-# isn't actually dead from Fusion Tables.  See issue 303 for an example of
-# the result of that removal.  
-#proguard.config=proguard.cfg
+# Enable proguard.
+proguard.config=proguard.cfg

MyTracks/proguard.cfg

@@ -51,3 +51,15 @@
 -keep class * implements android.os.Parcelable {
   public static final android.os.Parcelable$Creator *;
 }
+
+# Needed by google-api-client to keep generic types and @Key annotations accessed via reflection
+
+-keepclassmembers class * {
+  @com.google.api.client.util.Key <fields>;
+}
+
+-keepattributes Signature,RuntimeVisibleAnnotations,AnnotationDefault
+
+# Needed by Guava
+
+-dontwarn sun.misc.Unsafe